Hydraulic pump



April 6, 1966 D. c. HALSEY 3,247,803

HYDRAULIC PUMP Original Filed March 20, 1963 4 Sheets-Sheet 1 m ifINVENTOR. jdyii 6', flax A ril 26, 1966 D. c. HALSEY 3,247,303

HYDRAULIC PUMP Original Filed March 20, 1963 V 4 Sheets-Sheet 2INVENTOR. -E- JNJ Y B QAA/LMA- 1 7a FIVE Vs A ril 26, 1966 D. c. HALSEY3,247,803

HYDRAULIC PUMP Original Filed March 20, 1963 4 Sheets-Sheet 3 April 26,1966 0 riginal Filed March 20, 1963 D. c. HALSEY 3,247,803

HYDRAULIC PUMP 4 Sheets-Sheet 4.

Steer/Mg UNIT j INVENTOR.

United States Patent 6 Claims. (Cl. 103-136) This application is adivision of my copending application, Serial Number 266,569, filed March20, 1963.

This invention relates to improvements in hydraulic pumps, particularlyhigh pressure pumps suitable for use with automobile power steeringmechanisms.

An important object of the present invention is to provide an improvedbalanced pump of the above character comprising a housing containing acylindrical pumping cam of out-of-round cross section. A cylindricalrotor mounted within the cam cooperates with the latter to provide apair of diametrically spaced inlet chambers and another pair ofdiametrically spaced pumping chambers associated respectively withcorresponding pairs of inlet and pumping arcs at the inner surface ofthe cam. The rotor carries a plurality of radially shiftable pumpingelements such as slippers or rollers in fluid pumping and sealingengagement with the inner cylindrical surface of the cam, which latteralso comprises a separate constant radius dwell or sealing arc spacingeach pair of proximate ends of the pumping and inlet arcs and has a pairof inlet ports extending radially through its sidewall to connect thetwo inlet chambers with an annular fluid inlet header extendingcoaxially around the outer surface of the cylindrical cam.

By virtue of the annular inlet header enclosing the outer surface of thecam, free interchange of fluid between the inlet ports and also thesupply of fluid to both inlet ports are readily accomplished regardlessof constantly changing pump speeds. In consequence, means are avoidedfor prorating the inlet fluid to the two inlet chambers,

as for example by varying the size of the radial inlet ports. Theprovision of the annular inlet header also renders the pump suitable foruse with either an odd or even number of pumping elements withoutnecessitating any change in the dimensions of the cam or ports or otherfeatures of the pump.

Another object is to provide such a pump wherein the inlet ports arelocated to assure a predetermined circulation of fluid in the inletheader, thereby to stabilize the temperature around the periphery of thecam to achieve efiicient operation of the pump and reduction in noise byminimizing localized differential heating and consequent warping of thepump elements.

As the normal automobile operating speed range increases, the demand fora compact fast-acting power steering unit also increases. This demand isintensified as the road clearance and under-the-hood space for enginedriven accessories decrease in accordance with the trend toward morecompact and streamlined automobiles. This trend has in turn created ademand for a compact fluid pump capable of operating at high speed andat high fluid pressure for use With the power steering gear. Powersteering pumps known heretofore, which have been adequate for use atcomparatively low pressures, are noisy, and subject to excessive wear atthe high pressures now required. Wear with consequent noise, isparticularly objectionable between the pumping elements and cam. Wherethe curvature of the cam is too sharp at any region of the pumping arefor example, the pumping element is urged against the pumping camsurface with such force that the latter is scored, with consequent noiseand excessive wearing of the parts during operation under load at highspeed. Likewise during such operating conditions, where the camcurvature is too sharpat any region of the inlet arc, the pumpingelements often fall away from the pumping cam surface and thereafterabruptly contact the latter with resulting-noise and excessive wear.

It is accordingly another object to provide an improved vehicle powersteering pump which avoids the above objections and has an improved camcontour along the pumping and inlet arcs, and 'in particular to providesuch a cam having a contour which is characterized by a moderatecurvature and gradual changes in curvature throughout its length and anexceptionally smooth transition between the pumping and inlet cam arcsand the intermediate sealing cam arcs of the constant radius, whereby acomparatively noiseless and long wearing power steering pump is providedfor use under the most severe operating conditions of a modernautomobile.

Other objects are to provide an improved compact arrangement in anautomobile power steering pump and flow control valve for regulating therate of flow of pressurized fluid from the pump to the power steeringmotor, which is particularly efficient in operation, simple in construc'tion, and economical to manufacture and assemble.

substantially along the line 1-1 of FIGURE 3.

FIGURE 2 is a reduced transverse sectional view with reservoir coverremoved, taken in the direction of the arrows substantially along theline 22 of FIGURE 1.

FIGURE 3 is a sectional view taken in the direction of the arrowssubstantially along the line 3--3 of FIG- URE 1.

FIGURE 4 is a fragmentary sectional view taken in the direction of thearrows substantially along the line 4-4 o-f FIGURE 3.

FIGURE 5 is a right end view of the pump illustrated in FIGURE 1 withthe pulley removed.

FIGURE 6 is a fragmentary sectional view taken in the direction of thearrows substantially along the line 6-6 of FIGURE 5.

FIGURE 7 is a reduced transverse sectional view I through the pumpingcam element, illustrating the inlet and pumping arcs spaced by theconstant radii dwell arcs.

It is to be understood that the invention is not limited in itsapplication to the details of construction and arrangement of partsillustrated in the accompanying drawings, since the invention is capableof other embodiments and of being practiced or carried'out in. variousways. Also it is to be understood that the phraseology or terminologyemployed herein is for the purpose of description and not of limitation.

Referring to the drawings, an embodiment of the present invention isillustrated by way of example comprising a cast steel housing 10 havinga large bore 11 opening at one end and a smaller coaxial bore 12 openingat the opposite end through 'a thickened portion 10a of the housing. Thebores 11 and 12 open inwardly into an enlarged intermediate chamber 13containing a hollow cylindrical cam 14 having an outer cylindricalsurface closely confined at one end within bore 11. A roller 15 coaxialwith the outer surface of cam 14 is contained within the hollow cam andis splined on a central rotor shaft 16 coaxial with the bores 11 and 12so as to rotate with shaft 16 and slide axially'thereon. Extendingcoaxially in opposite directions from the rotor 15 are bearing portions16a and 16b of the shaft 16 journaled within bearings 17 and 18respectively, the latter bearing being supported within the housingportion a which is adapted to withstand the major side loading of thebearing 18 resulting from operation of the pump under load. The shaftextension 1612 projects outwardly through a suitable seal 19 containedwithin housing portion 16a and is keyed to the hub 20 of a power drivenpulley 21.

The interior cylindrical surface of cam 14 is out of round andcooperates with rotor 15 to provide a pair of diametrically opposedinlet chambers 22 and a pair of diametrically opposed pumping ordischarge chambers 23 mutually spacing each other, FIGURE 2. Theperiphery of rotor 15 is provided with a plurality of cylindricalaxially extending and radially outward opening notches 24 for acorresponding number of cylindrical rollers 25 of circular crosssection. The present pump is designed to employ approximately eleven ortwelve rollers 25 which make sliding and sealing engagement with theinterior surface of cam 14 and with the trailing surface of theassociated notch 24 in consequence of the fluid pressure and centrifugaland inertia forces acting thereon during operation of the pump.

The opposite axial ends of cam 14 and rotor 15 as well as the axiallyinner surface of housing portion 10a lie in transverse planesperpendicular to the rotor axis, the right ends of cam 14 and rotor 15being spaced from housing portion 10a by an annular Wear plate 26 havingthe same outside diameter as cam 14. The outer surfaces of cam 14 andwear plate 26 are spaced from the inner circumference wall of housing 10to provide an annular inlet header 27 extending coaxially around theaxis of rotor shaft 16 and communicating with the inlet chamber 22 via acorresponding pair of inlet ports 28 extending generally radiallythrough cam 14.

The bore 11 at the left end of housing 10 is provided with a closureincluding an annular pressure plate 29 having a plane axial inner endsurface abutting the left ends of cam 14 and rotor 15 and having anouter cylindrical surface closely fitting within bore 11 in slidingrelation. The closure for bore 11 also includes an annular cap orclosure member 30 seated on an annular axial extension 31 of plate 23.Suitable annular seals 32 and 32a between the juxtaposed surfaces ofextension 31 and cap 30 and also between cap 30 and the inner wall bore11 prevent axial loss of pressurized fluid between these members. Theconfronting surfaces of plate 29 and cap 30 are formed with matinggrooves 33 and 34 which cooperate to provide an annular discharge headerextending coaxially around the axis of rotor shaft 16 and communicatingwith the discharge chambers 23 via a corresponding pair of dischargeports 38 extending axially through plate 29. A coil spring 35 within theheader 33, 34 urges plate 29 to the right against the end surfaces ofcam 14 and rotor 15. Leftward movement of cap 30 is prevented by anannular snap ring 36 partially embedded within the interior surface ofbore 11.

A pair of diametrically spaced locating dowels 37, FIG- URES 2 and 4extend slidably through plate 29, cam 14 and wear plate 26 and areconfined at their axially opposite ends in housing portion 10a and capclosure 30. Thus fluid pressure within discharge header 33, 34 urgesmembers 29, 14 and 26 closely together and toward the inner wall ofhousing portion 10a to prevent fluid leakage between these parts with aforce proportional to the pump discharge pressure, which force is alsoproportional to the tendency for fluid leakage. At the same time,thermally induced dimensional changes in these parts, particularlybetween cam 14 and rotor 15, is readily accommodated. Furthermore, theaxial dimension of rotor 15 and cam 14 may feasibly be almost identicalto achieve optimum pump efliciency by minimizing a bypass flow of fluidaround the ends of the rotor 15 during operation of the pump. Also inaccordance with the construction shown and as explained more fullybelow, axially directed forces on the cam 14 and rotor shaft 16 aresubstantially in balance at all times. Small transient unbalanced forcesare assumed by the annular thrust bearing 39 having its innercircumference closely confined within a mating groove in shaft 16 andhaving an outer portion confined between plate 26 and housing portion10a.

Extending radially from bore 11 and header 27 is an extension 1% of thehousing 10 which contains a bypass bore 40 parallel to the coaxial bores11 and 12. An axially slidable single-land spool valve 41 within bore 40normally closes a supply conduit 42 extending radially inwardly from acentral portion of bore 40 into the inlet head 27. The valve 41 has ahollow interior 43 opening to the right in FIGURE 1 and containing acoil spring 44 under compression between a closure plug 45 and the leftend of the interior 43. The closure 45 seals the right end of bore 40,which extends completely through housing extension 10b, and is retainedagainst rightward movement by snap ring 46 embedded within the interiorwall of bore 40. The left end of valve 41 is reduced at 47 to provide aradial shoulder 48 and contains four radial metering ports 49 openinginto the interior 43 of valve 41. The left end of bore 40 is closed by aclosure plug 50 retained against leftward movement by snap ring 51partially embedded within the inner wall of bore 40. The plug alsoprovides an integral axially inwardly directed stop 52 which abuts valve41 to limit its leftward movement.

Pressurized fluid from discharge header 33, 34 is conducted by agenerally radially extending duct 53 in housing 1%), FIGURE 3, to anenlargement 54 of bore 40 at the left end of valve 41. Pressurized fluidfrom conduit 53 enters the left end of bore 40 at the enlargement 54,then flows through metering orifices 49 at a substantially constant rateof approximately two gallons per minute into the interior 43 then to anenlargement 5511 at the right end of bore 40, from whence the meteredfluid is conducted via transverse duct 55 to duct 56 within housing 10and an exterior conduit 57 to the vehicle power steering unit, FIGS. 5and 6.

Extending around the circumference of the housing 10 is an annulargroove and support 58 on which is supported the flanged end 59 of a cupshaped container 60. The latter encloses the left end of housing 10 andcooperates therewith to form a reservoir 61 into which the fluid fromthe power steering unit may be returned, FIG. 5. Fluid leakage betweenthe support 58 and the juxtaposed side walls of the container isprevented by an O-ring 62.

In order to supercharge the flow of fluid into the inlet header 27 viasupply conduit 42, the latter is provided with a venturi restriction 63at the opening of a duct 64 in communication with the reservoir 61. Thebypass bore enlargement 55a and transverse duct 55. are also connectedby means of a pressure relief conduit 65 in housing portion 10b with anaxially extending threaded conduit 66 opening into the reservoir 61 andnormally closed by a pressure relief valve 67 which may be ofconventional construction.

In operation of the structure described, upon the application of powerto pulley 21, rotor 15 is rotated in the direction of the arrow, FIGURE2, to draw fluid into the inlet chamber 22 from header 27 via the radialinlet ports 28 by operation of the rollers 25. The fluid drawn into theinlet chambers 22 is carried clockwise to the discharge chambers 23 andis then forced into the discharge header 33, 34 via the axial dischargeports 38. In order to balance the pump hydraulically, axially inwardlyopening notches 68 shaped identically with the discharge ports 38 areformed in the surface of the wear plate 26. Small tapered precompressionnotches 28a and 38a are provided at the trailing edges of the inletports 28 and in the leading edges of the discharge ports 38 toaccommodate inertial effects of the fluid and to minimize cavitation andnoise during pump operation in accordance with customary practice. Alsoby the construction described, leakage from discharge header 33, 34returns to inlet header 27. Endwise leakage at bearing 17 returns to thereservoir 61. Endwise leakage at bearing 18 is collected in annularchamber 69 upstream of seal 19 and is returned via duct 70 to inletheader 27.

As the discharge pressure increases at high pump load, as for exampleduring a parking maneuver when the pump is normally operating at lowspeed, the resulting high pressure in discharge header 33, 3d urgespressure plate 29 more firmly against the juxtaposed ends of cam 14 androtor to compact these members more tightly between plates 26 and 29than when the pump is under light load, as for example during straightahead steering when the pump is usually operating at high speed. Thehigh pressure fluid discharged from header 33, 34 is conducted viaconduit 53 to the inlet or upstream end 54 of bypass bore 40, wherebyfluid at the rate of approximately two gallons per minute is supplied tothe power steering unit via metering ports 49 as described above. Thepressure of the pump discharge in excess of the two gallons per minuteflow will act on the left end of valve 41 to move the latter rightwardagainst the tension of spring 44 until shoulder 48 establishescommunication between supply conduit 42 and the upstream inlet enlargement 54. The pressure at which valve ll opens to bypass the pumpdischarge into supply conduit 42 will of course be determined by thetension of spring 44. In the event that the pump discharge pressureexceeds a predetermined limit downstream of ports 29, pressure reliefvalve 67 will open to discharge directly from duct 55 into reservoir 61.

During normal operation of the pump, the bypass flow from enlargement 54into supply conduit 42 will result in a reduced pressure at the venturi63 whereby the flow of fluid from reservoir 61 through duct 64 and intoinlet header 27 will be accelerated to supercharge the flow to the inletports 28. In this regard it is to be noted that the opening of duct 64into supply conduit 42 is adjacent the juncture of the latter with inletheader 27 to assure optimum supercharging. Also the two diametricallyopposed inlet ports 28 are arranged asymmetrically with respect to thesupply conduit 42, the port 28 which is located on the clockwise side ofduct 42, FIGURE 2,

being more remote than the diametrically opposed inlet port 28, so thatthese two ports may both be of the same size and yet receive the sameamounts of inlet fluid. The length of the path of the inlet flow inheader 27 to the inlet port 28 in the same clockwise direction as therotation of rotor 15 is determined with respect to the length of thepath of the corresponding inlet flow in the opposite direction to theother inlet port 28 so that the amount of flow to each inlet port 28from supply conduit 4-2 is approximately balanced. The ports 28 arelocated however so that a portion of the inlet flow into the port 28 atthe counterclockwise side of supply conduit 42 will enter in a clockwisedirection from the far side of the inlet header 2'7. The amount of suchflow will vary in accordance with the speed of rotation of the pump, butwill .always be adequate to prevent stagnation of fluid within the farside of the inlet header 27.

In consequence of the arrangement described, the fluid flow withinheader 27 will serve as a coolant to minimize localized overheating ofthe pump and assure a more uniform thermal expansion and contraction ofits parts. In

addition, a portion of the header 2'7 connecting the inlet ports 28 atthe side of the header opposite the supply conduit 42 assures fluidsupply to both ports 28 and enables the use of the same earn element 14and inlet ports 28 with a rotor having either eleven or twelve pumpingelements 25.

Referring to FIGURE 7, the contour of the interior cam surface ofelement 14 is illustrated where points I and I designate the beginningand end of a fluid inlet arc I 1 along which the rollers 25 rise or moveradially outwardly a total radial distance H from the circumference of acircle of small radius C to the circumference of a concentric circle oflarger radius C The are I 1 represents a second inlet arc, whereas thearcs D D and D D represent first and second pumping arcs along which therollers 25 fall the radial distance H, the arcs D 1 and D 1 representdwell arcs of constant radius C and the arcs I D and I D represent dwellarcs of constant radius C As the rollers 25 rise along each inlet arc Ill and I 1 upon clockwise rotation of the rotor 15, fluid is drawnthrough the associated inlet port 28 into the inlet chambers 22comprising the spaces between the rotor '15 and each inlet arc. Thefluid is then carried clockwise along the length of the dwell arcs I Dand I D and, thereafter as the rollers fall along each pumping arc D Dand D D is forced outwardly through the discharge ports 38 from thepumping chambers 23 comprising the spaces between the rotor 15 and eachpumping arc.

In order to minimize noise and Wearing in the highspeed high-pressurepump, the inlet and pumping arcs must blend smoothly at their oppositeends with the curves of constant radius C and C Also the curvature ofthe cam 14 must satisfy the conditions that the rollers 25 will followthe cam surface closely without changing direction too abruptly at anypoint therealong, so as to avoid excessive wearing of the parts andnoise during high-speed high-pressure operation of the pump. Thus therollers 25 must not fall away from the inlet arc portions of increasingradius and thereafter strike the cam contour with excessive force, norshould the rollers be urged with excessive force against the pumping arcportions of decreasing radius.

Any cunve of finite length, such as profile of one of the inlet orpumping cam arcs, can be approximated by the polynominal:

where y is the ordinate and x is the abscissa in the cartesiancoordinate system.

The corresponding curve in polar coordinates suitable for representingthe cam contour about the center C of the circles C and C is:

where for the sake of convenience the unit. of radial measurement is H,the unit of angular measurement is the angle from the center C subtendedby the inlet or pumping cam arc involved, R is the radial measurementfrom the circumference of inner circle C to the circumference of outercircle C and A is the angular measurement abou the center C in thedirection of decreasing R. Thus for the pumping arcs, A is measured fromthe point D to the point D and from the point D to the point D For theinlet cam arcs, A is measured from the point I to the point I and fromthe point I to the point I It is also apparent that the radial velocityof a roller with respect to its angular displacement as it moves alongthe cam arc is represented by the differential of R with respect to A,that is R=dR/dA. Similarly radial acceleration R"=d R/dA and the rate ofchange of acceleration with respect to changes in A, referred to Aconcept of the present invention has been to provide inlet and pumpingcam contours such that their terminals blend so smoothly with thecircles C and C that as a roller 25 leaves the constant radius C orrides onto the constant radius C the radial velocity R in each case willbe zero to avoid sudden stress and resultant wear and noise. Similarlyinertial and vibratory forces resulting from acceleration R" and therate of change of acceleration or jerk R' are avoided at the terminalpoints of the inlet or pumping cam arcs it both R" and R' are also zero.We accordingly have as terminal conditions:

When A=0; R=1, and R'=R=R"'=0.

These eight conditions enable determination of the eight constants inthe equation:

Additional terms can be added by extending the terminal conditions toinclude R"=0, etc., but the additional terms have negligible effect onthe operating efficiency of a power steering pump of the characterdisclosed at the terminals of the inlet and pumping cam arcs andnecessarily increase the maximum radial acceleration R" of rollersriding on the cam surface at some point between the terminals. Thus theadditional terms are objectionable because, in order to minimize wearingbetween the rollers and cam surface, the minimum force therebetweenresulting from radial acceleration is desired. This is especially truewith a balanced pump of the type shown having two inlet ports and twodischarge ports, where the rise or fall H must be accomplished in acomparatively small arcuate segment. On the other hand, less than theeight terms shown results in objectionable noise and wear at theterminals during high speed operation, because if acceleration Rf andjerk R are not zero at the terminals, the resulting sudden change inradial velocity and acceleration will cause infinite jerk at theterminals. By reducing jerk R to zero, the transitions between the inletand pumping cam contours and the portions of constant radius C and C areaccomplished with optimum smoothness without unduly increasing themaximum acceleration R" at any intermediate portion of the cam contours.

It is apparent from the terminal condition A= when R l, FIGURE 7, that[7 :1 in Equation 3. It is also obvious that [i -=0 for values of 11:1,2 or 3, because, for the aforesaid values of n, dR/dA =0 when A=0. Thusb =b =b =0 and Equation 3 reduces to:

From the remaining four terminal condition R=R:R"=R=0 when A=1, the fourcoeflicients b b b and b can be readily determined by simultaneousequations as follows: b4=35, [95:84, b6-|70, and b7=20.

Equation 4 becomes:

Equation 5 determines either a pump or an inlet cam are wherein, notonly is an exceptionally smooth transition with the seal arcs ofconstant radius obtained, but also a moderate curvature characterized bygradual changes throughout the length of the cam arc is obtained enablesproduction of a highly efficient, quietly operating, and long wearingpower steering pump.

By virtue of the units of A and R specified above, each value of R alongthe curve of one of the pumping or inlet cam arcs will determine one andonly one corresponding value for A. For a pump of the type shown, it hasbeen found adequate to calculate the value of R at each twenty minutesof arc. Inasmuch as the total angular measurement from D to D in FIGURE7 is 70", each of arc (one-third of a degree) represents (20/ 3) (1/ 70=2/ 21 of the unit angular measurement employed in Equation 5. Thegreater the angular measurement of the pumping and inlet arcs, the lesswill be the acceleration forces on the rollers. The smallest feasibleinlet arc has been found to be approximately 58 for a pump of the typeshown where the distance H is approximately 10% of the radius of circleC This limit is determined by the magnitude of the rise H, the operatingpressure and speed of the pump, and the related factorthe centrifugalforce urging the rollers 25 into sealing engagement with the innersurface of cam 14. If the inlet arc is so small that the roller cannotfollow the cam surface, the sealing engagement is lost and noise andpump inef'ficiency will result. A somewhat smaller pumping arc can beemployed, the limit again being determined by the fall H and by theoperating speed and pressure of the pump.

The maximum value of R in Equation 5 is the unit distance H between theinner and outer circles C and C The value of R corresponding to eachassigned value of A can readily be converted to any other unit ofmeasurement by multiplying the value obtained from Equation 5 by thetotal value of the distance H in the other unit, as for example thevalue of H measured in inches. In the present instance, the contour ofthe pumping cam arc D D is identical with the contour of arc D D whereasthe contours of the inlet cam arcs I 1 and 1 1 are mirror images of arcD D Having thus described my invention, I claim:

1. In a fiuid pump, a housing, a rotor rotatable within said housing, acam element extending around said rotor and cooperating therewith toprovide two pumping chambers and two inlet chambers mutually spacingeach other circumferentially, said cam element comprising a pair ofpumping cam arcs associated with said pumping chambers respectively, apair of inlet cam arcs associated with said inlet chambers respectively,and a separate constant radius sealing cam are connecting the ends ofeach inlet cam arc with the proximate ends of the next adjacent pumpingcam arcs, said pair of inlet cam arcs and said pair of pumping cam arcsmutually spacing each other circumferentially, inlet and outlet portsfor supplying fluid to said inlet chambers and for discharging fluidfrom said pumping chambers respectively, a plurality of pumping elementscarried by said rotor and cooperable with said cam element to pump saidfluid from said inlet chambers to said pumping chambers, each inlet andpumping cam are being defined by a seventh power polynomial R and Abeing radial and angular measurements respectively and b b b b b beingconstants such that the first, second, and third derivatives of R withrespect to A are each equal to Zero at the terminals of each inlet andpumping cam arc, the radius at the beginning and ending of each inletand pumping cam are being equal to the radius of the adjacent sealingcam arc.

2. In a fiuid pump, a housing, a rotor rotatable about an axis withinsaid housing, a cam element extending around said rotor and cooperatingtherewith to provide two pumping chambers and two inlet chambersmutually spacing each other circumferentially, said cam elementcomprising a pair of pumping cam arcs of variable radius associated withsaid pumping chambers respectively, a pair of inlet cam arcs of variableradius associated with said inlet chambers respectively, and a separateconstant radius sealing cam are connecting the ends of each variableradius inlet cam arc with the proximate ends of the next adjacentvariable radius pumping cam arcs, said pair of variable radius inlet camarcs and said pair of variable radius pumping cam arcs mutually spacingeach other circumferentially, the constant radius of the sealing cam areat the beginning of each variable radius pumping cam are being greaterthan the constant radius of the sealing cam are at the end of thatpumping cam arc, inlet and outlet ports for supplying fluid to saidinlet chambers and for discharging fluid from said pumping chambersrespectively, a plurality of pumping elements carried by said rotor andcooperable with said cam element to pump said fluid from said inletchambers. to said pumping chambers, each variable radius cam are beingdefined by the polynomial R=l35A +84A -7OA +20A R being the radialmeasurement from the smaller radius sealing cam arc to the larger radiussealing cam arc at the ends of the associated variable radius cam arc,the unit of radial meas urement being the radial difference between saidsealing cam arcs at said ends of the associated variable ratio cam are,A being the angular measurement about said axis in end of the associatedvariable radius cam arc, and the unit 9 of angular measurement being theangle from said axis subtended by the associated variable radius camarc.

3. In a fluid pump, a housing, a rotor rotatable within said housing, acam element extending around said rotor and cooperating therewith toprovide an inlet chamber and a discharge chamber, said cam elementhtving an inlet cam arc and a discharge cam are associated with saidinlet chamber and discharge chamber respectively, inlet and dischargeports for supplying fluid to said inlet chamber and for dischargingfluid from said discharge chamber respectively, a plurality of pumpingelements carried by said rotor in sliding engagement with said camelement to pump said fluid from said inlet chamber to said dischargechamber, the radius of said inlet ca-m arc progressively increasing inthe direction of rotor rotation and being defined by the seventh powerpolynomial wherein R and A are radial and angular measurementsrespectively, and b b b b are constants such that the first, second, andthird derivatives of R with respect to A are each equal to zero at bothends of said inlet cam arc.

4. In a fluid pump, a housing, a rotor rotatable within said housing, acam element extending around said rotor and cooperating therewith toprovide an inlet chamber and a discharge chamber, said cam elementhaving an inlet cam arc and a discharge cam are associated with saidinlet chamber and discharge chamber respectively, inlet and dischargeports for supplying fluid to said inlet chamber and for dischargingfluid from said discharge chamber respectively, a plurality of pumpingelements carried by said rotorin sliding engagement with said camelement to pump said fluid from said inlet chamber to said dischargechamber, the radius of one of said cam arcs progressively changing inone direction only from one end thereof to its other end and beingdefined by the seventh power polynomial R=b +b A+b A +b A b A", whereinR and A are radial and angular measurements respectively and b b b b7are constants such that the first, second, and third derivatives of Rwith respect to A are each equal to zero at both said ends of said onecam arc.

5. In a fluid pump, a housing, a rotor rotatable about .an axis withinsaid housing, a cam element extending around said rotor and cooperatingtherewith to provide an inlet chamber and a discharge chamber, said camelement having an inlet cam arc and a discharge ca-m arc associated withsaid inlet chamber and discharge chamber respectively, inlet anddischarge ports for supplying fluid R1 135A |84A A +20A wherein R is theradial measurement starting from zero at the small radius end andmeasuring outwardly toward the large radius end of said inlet cam arc,the unit of radial measurement is the radial difference between saidends, A is the angular measurement about said axis in the direction fromthe large radius end to the small radius end of said inlet cam arc, andthe unit of angular'measurement is the angle from said axis subtended bysaid inlet arc.

6. In a fluid pump, a housing, a rotor rotatable about an axis withinsaid housing, a cam element extending around said rotor and cooperatingtherewith to provide an inlet chamber and a discharge chamber, said camelement having an inlet cam arc and a discharge cam arc associated withsaid inlet chamber and discharge chamber respectively, inlet anddischarge ports for supplying fluid to said inlet chamber and fordischarging fluid. from said discharge chamber respectively, a pluralityof pumping elements carried by said rotor in sliding engagement withsaid cam element to pump said fluid from said inlet chamber to saiddischarge chamber, the radius of at least one of said cam arcsincreasing progressively from one end to the other and being defined bythe polynomial wherein R is the radial'measurement starting from zero atthe small radius end and measuring outwardly toward the large radius endof said one cam arc, the unit of radial measurement is the radialdiflerence between said ends, A is the angular measurement about saidaxis in the direction from the large radius end to the small radius endof said one cam arc, and the unit of angular measurement is the anglefrom said axis subtended by said one arc.

References Cited by the Examiner UNITED STATES PATENTS 1,271,585 7/1918Klise 103-136 2,378,390 6/1945 Bertea 103136 2,498,530 2/1950 Cooke103-136 3,204,567 9/1965 Krawacki 103-139 SAMUEL LEVINE, PrimaryExaminer.

1. IN A FLUID PUMP, A HOUSING, A ROTOR ROTATABLE WITHIN SAID HOUSING, A CAM ELEMENT EXTENDING AROUND SAID ROTOR AND COOPERATING THEREWITH TO PROVIDE TWO PUMPING CHAMBERS AND TWO INLET CHAMBERS MUTUALLY SPACING EACH OTHER CIRCUMFERENTIALLY, SAID CAM ELEMENT COMPRISING A PAIR OF PUMPING CAM ARCS ASSOCIATED WITH SAID PUMPING CHAMBERS RESPECTIVELY, A PAIR OF INLET CAM ARCS ASSOCIATED WITH SAID INLET CHAMBERS RESPECTIVELY, AND A SEPARATE CONSTANT RADIUS SEALING CAM ARC CONNECTING THE ENDS OF EACH INLET CAM ARC WITH THE PROXIMATE ENDS OF THE NEXT ADJACENT PUMPING CAM ARCS, SAID PAIR OF INLET CAM ARCS AND SAID PAIR OF PUMPING CAM ARCS MUTUALLY SPACING EACH OTHER CIRCUMFERENTIALLY, INLET AND OUTLET PORTS FOR SUPPLYING FLUID TO SAID INLET CHAMBERS AND FOR DISCHARGING FLUID FROM SAID PUMPING CHAMBERS RESPECTIVELY, A PLURALITY OF PUMPING ELEMENTS CARRIED BY SAID ROTOR AND COOPERABLE WITH SAID CAM ELEMENT TO PUMP SAID FLUID FROM SAID INLET CHAMBERS TO SAID PUMPING CHAMBERS, EACH INLET AND PUMPING CAM ARC BEING DEFINED BY A SEVENTH POWER POLYNOMIAL 